The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Modern vehicles are highly dependent on proper operation of an electric power generation and storage system. The number of electrical devices has been rapidly increasing in the last two decades, and this trend will accelerate. The vehicle electric power system is required to supply sufficient power not only to safety related systems such as rear window defogger, anti-lock braking and stability enhancement system, but also to comfort, convenience and entertainment features such as air conditioning, seat heating, audio and video systems. The advent of new technologies such as X-by-wire is putting additional demand on the battery. Consistent power flow from an electric power storage device, such as a battery, is critical for maintaining proper vehicle operations. Battery problems lead to customer dissatisfaction and service issues. Therefore, there is a need to monitor and control the ability of the battery to deliver power throughout various vehicle operation modes and throughout battery life.
An essential function of automotive batteries is to deliver high power in short periods, for instance, during engine cranking. Modern vehicle control systems utilize an electric power management system to balance power demanded and supplied during vehicle operation and to provide engine starting power. Battery state is an essential element of any electric power management system. Due to the electrochemical nature of battery devices, numerous factors affect the battery state, thus making determination of battery status complicated. The battery state is represented by state of charge (SOC) and state of health (SOH). The SOC represents the stored power/energy available, and the SOH is an indication of power capability and battery capacity. To achieve accurate power management, both battery SOC and SOH should be taken into account.
One known approach to vehicle electric power management for load shed and idle boost is based only on an index of battery state of charge. Other power management systems and methods have attempted to predict battery cranking capability based on battery cranking current or voltage. These systems require a high current sensor to measure battery current during cranking (e.g., 800-1000 Amps). Furthermore, there is no method identified to determine a threshold of cranking current or voltage for power management that takes into account both battery SOC and SOH. At least one method used for power management on a hybrid vehicle is based on battery model parameters that are identified during normal vehicle operation. However, real-time battery model parameter identification during normal operation requires the battery voltage and current signals to satisfy the condition of persistency of excitation, which is usually not applicable to conventional vehicles. Furthermore, the computational cost of such a method is high because it requires data acquisition and signal processing at a high sampling rate.
Therefore, there is a need for a cost-effective monitoring and control system for an electric power storage device to achieve accurate and reliable power management, taking into account both battery state of charge (SOC) and state of health (SOH), to address the aforementioned concerns.